1. Field of the Invention
The present invention relates to a system for electrically driving a heavy-duty materials handling apparatus, and in particular to a system for using a switched reluctance motor for electrically driving one or more wheels of a heavy-duty industrial materials handling vehicle, or a vehicle for other industrial applications.
2. Description of the Related Art
Mining, earth-moving, forestry, construction, and transportation industries, among others, use large, heavy-duty equipment for handling various types of materials, in various forms ranging from loose material, such as dirt or rocks, to large heavy objects, such as containers. The materials handling equipment may be self-propelled mobile vehicles or stationary equipment. An example of a heavy-duty materials handling mobile vehicle is a loader, commonly used in the mining industry for scooping up loose material and transporting the material to a truck for transport. An example of a stationary material handler is a jib crane used for log stacking. Numerous other forms of heavy-duty materials handling equipment are known, such as wheel dozers, stackers, straddle hoist cranes, and side porters. The mobile vehicles are typically off-road rubber-tired vehicles, where “rubber” is the commonly used name for various elastomeric materials used for tires, without limiting those tires to ones that contain natural rubber. Other forms of heavy-duty industrial vehicles include locomotives.
Historically, such rubber-tired heavy-duty equipment used diesel engines, with mechanical drive systems or transmissions, and gearing to drive the wheels of the vehicles. However, approximately fifty years ago, Le Tourneau, Inc., the assignee of the present invention, introduced electric drive systems to replace the mechanical drive systems.
The advantages of an electric drive system over the conventional drive have been proven by years of successful service of log stackers, front-end loaders, haul trucks and other heavy-duty material and container handling equipment.
In conventional electric drive machines, the utilization of solid-state power conversion and control, coupled with digital management gives additional advantages, such as reliability and ease of maintenance.
Digital control and management modules of conventional electric drive machines keep track of all the machine systems, producing controls for the electrical and hydraulic systems, commands for the engine and traction systems, and feedback, history and status information for all the systems. A display screen and keypad control may allow automatic and requested information to be displayed for a vehicle operator.
However, conventional electric drive systems have their own disadvantages, frequently related to the complexity of manufacture, operation, and maintenance of the electric traction drive motors, which conventionally have been alternating current (AC) or direct current (DC) motors.
Switched reluctance (SR) motor technology is also well known. Switched Reluctance Drives Ltd. of Harrogate, United Kingdom has developed multiple designs of SR motors or drives for various applications, including a 400 HP SR motor for a conveyor belt in a mining operation. In so far as known, however, there has been no application of SR motors to wheel-driven technology for large industrial or off-road vehicles, which present special problems in acceleration and deceleration as well as over-all control because of the size and weight of such vehicles, or for large industrial hoisting equipment, which present special problems in hoisting control because of the weight of material being hoisted.